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From: tower@inmet.UUCP
Newsgroups: net.math
Subject: Re: Another Prime Number Question With N
Message-ID: <5700005@inmet.UUCP>
Date: Wed, 15-May-85 06:54:00 EDT
Article-I.D.: inmet.5700005
Posted: Wed May 15 06:54:00 1985
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Nf-From: inmet!tower    May 15 06:54:00 1985


> /**** inmet:net.math / ihnet!eklhad /  9:33 am  May  7, 1985 ****/
> 	How many primes, when written in base 10,
> also produce prime sub-numbers (looking at the first n digits)?
> For example: 7193 is in the set, since
> 7, 71, 719, and 7193 are all prime.
> The list begins: 3, 5, 7, 31, 37, 53, 59, 71, 73, 79, 
> 311, 313, 317, 373, 379, 593, 599, ...
> Is the list infinite?
> If so, can anyone prove it.
> If not, and I conjecture not, what is the largest such number?
> Anyone with some time (personal and computer) can enjoy this one.
> Karl Dahlke    ihnp4!ihnet!eklhad

Ok, now that we're looking at base 10, lets generalise the problem:

For what bases is the list (defined above) for that base infinite?

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